Anti-China activists here have lined up events for today to "celebrate" what they expect will be a favourable ruling on the Philippines' landmark case to challenge China's vast claims in the South China Sea.
But calmer heads have cautioned against euphoria, as it is still possible that the decision may not go fully in Manila's favour.
Leaders of about a dozen groups that have been organising protests over what they claim to be China's efforts to seize Philippine territories plan to hold a "victory party" early this afternoon. Thousands of balloons in the red, blue and yellow colours of the Philippine flag will be released over Manila Bay.
A statement said Filipinos in New York, Washington, Los Angeles, San Francisco, the Mariana Islands, Vancouver, Tokyo, Milan, Paris and London will hold rallies in front of Chinese missions in these places.
The leftist New Nationalist Alliance staged a demonstration yesterday in front of the Chinese Embassy in Manila, and vowed to return today. The group demanded that China do a "Chexit" and pull its forces out of Scarborough Shoal as well as parts of the Spratly Island chain that fall inside the Philippines' so-called Exclusive Economic Zone.
Legal experts believe the 117- year-old Permanent Court of Arbitration at The Hague will hand down a verdict striking down the "nine-dash line", first introduced in 1947, that spans China's claims to over two-thirds of the 3.5 million sq km South China Sea.
The line, encircling an area roughly the size of Mexico, overlaps territories claimed by the Philippines, Vietnam, Malaysia, Brunei and Taiwan. China argues that its historic rights justify the line. But the Philippines insists that these rights cannot be used to define sea borders.
Sea borders, it argues, must start from land, under a United Nations treaty enforced in 1994 and ratified by China in 1996.
The Philippines says since the South China Sea is mostly sea, there is no land mass or clumps of islands and rocks there large enough to generate sea borders that will span the over 2 million sq km China is claiming with its nine-dash line.
"We celebrate a ruling that reinforces our rights over our own resources," Mr Vonz Santos, one of the leaders organising today's events, said.
But the Philippines is not assured of total victory. The court, for instance, may declare Taiwan-occupied Itu Aba, 416km west of the Philippines' coast, an island. That will expand Itu Aba's borders to the coast of the western Philippine province of Palawan.
The arbitral tribunal may also choose to withhold ruling on the maritime rights of reefs in the South China Sea that China has turned into islands over the last two years.
The Philippines' Foreign Ministry has promised a muted response to the court's ruling, as President Rodrigo Duterte has said he prefers to hold direct talks with China on jointly tapping resources in contested waters of the South China Sea.